Electrical switch and combination electrical resistor and switch

ABSTRACT

An actuator, coiled compression spring, and abutment surface or pair of stationary contact surfaces trap a contact roller. The spring shifts relative to the roller, assumes various contorted configurations, and whips the roller along actuator cam surfaces to stable roller positions. Also disclosed are means interlocking a shaft and switch actuator; a rotatable and axially movable switch actuator; and an actuator and shaft that snap together with means that prevent subsequent separation of the shaft and actuator.

United States Patent:

[72] Inventor Jack A. English Elkhart, Ind. [21 Appl. No. 838,755 [22] Filed July 3, 1969 [45] Patented Aug. 17, 1971 [73] Assignee CTS Corporation v Elkhart, Ind.

[54] ELECTRICAL SWITCH AND COMBINATION ELECTRICAL RESISTOR AND SWITCH 3,196,230 7/l965 Barden eta] 2,881,280 4/1959 Bardenetal 16 Claims, 14 Drawing Figs.

[52] (L8. Cl. 200/77, 4

200/68 338/193 ABSTRACT: An actuator, coiled compression spring, and b t t surface or i f t ti Contact Surfaces p a 15/18 'contact roller. The spring shifts relative to the roller, assumes [50] Field of Search 200/68, 76, various contorted configurations, and whips the roller along M; 338/200, 8 actuator cam surfaces to stable roller positions. Also disclosed 56 R f cud are means interlocking a shaft and switch actuator; a rotatable 1 e erences. I and axially movable switch actuator; and an' actuator and shaft UNITED STATES PATENTS v that snap together with means that prevent subsequent separal,877,923. 9/1932 Lucia 200/68 tion of the shaft and actuator.

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92- 56: I i Z A :5;

27 l n l l r. I i I I l M576 686.]

PATENTEDAUGIYIBH 3,600,533

sum 1 0F 2 FIGURE l FIGURE 2 JACK A. ENGLISH wy-30 ATTORNE PATENIEDAUBIYIBYI 3.600.533

SHEET 2 OF 2 FIGURE IO FIGURE H FIGURE 13 FIGURE l2 INVENTOR JACK A. ENGLISH FIGURE 14 W 25014101 ATTORNEY ELECTRIC ALSWITCH AND-COMBINATION ELECTRICAL RESISTOR ANDSWITCII This invention relates :generally to electrical controls and, more particularly, toan electrical switchand to a combination variable resistance and electrical switch control.

Theprior art includes many different typesof electrical switches-and variable resistance controls combined with such switches. In order to clarify the meaning of terminology used herein it is to be understood that the term electrical control is used generically to designate devices for controlling the current orvoltage in an electrical circuit and that an electrical switch" as well as a combination variable resistance and electrical switch controlFare a species of electrical controls." It is well known that a snap-action switch must be capable of very rapidly making and breaking an electrical circuit and that theswitch must betease-proof, that is, the switch must be designed so.that one or more movable contactors within the switch cannot be heldin a neutral or center position by carefully controlling or manipulating the switch actuating member. By'neutral position is meant a position where the ry for previous'applications could not pass extended life testsand could not operate in a satisfactory manner over an extended period of time whenrequired to switch heavy loads such as those encountered in modern consumer appliances and entertainment equipment. When.used in modern high power requirement situations, it has beenfound that such switches'permitted arcing to occur and destroy the movable and stationary contacts, that the temperaturerise within the switch was too high due to high contact resistance, or that inadequate mechanical clearances existed between conductive elements within the switch. In addition to the increasedloads that present day switches must handle,'problems are presented by the fact that such switches must occupy no'more volume than the prior art switches which they are to replace.

- Much effort has been expended in trying to ascertain the optimum configuration for a bridging contactor in'small, compactswitch. One prior art-design has used ball bearing type contactors, as illustrated for example in Ludwig Pat. No. 2,743,330'and Siiberg Pat. No. 3,032,620. Other designs have made use of knife 'blade or formed spring contactors as shown in Barden et al. Pat. No. 2,88 l ,280 and dumbbell-shaped contact rollers. In each of these designs, spring'means have been used to impart a snap-action movement to the contactor and to *bias'the bridging contactor into a stable position. In some instances, the bridging contactor has been a spring means.

whereas in other instances a separate spring element has been used to bias the bridging contactor. Each of these prior designs have required a relatively large number of "parts that mustbe assembled together and this has resulted in a complex and expensive switch assembly.

In. the particular species of electrical controls that include combination variable resistance and electrical switch controls, and particularly those of the type in which the. control operator is a rotatable shaft aswell as anaxially movable switch'actuator, the reliable and economical interconnection between such shaft and switch actuator has also been a continuing problem. It will, therefore, be appreciated. that it would be eliminated or reduced-and yet wherein such control may be readily andinex'pensive'ly fabricated. In addition, it would be extremely-desirable to provide means that would substantially prevent separation of an axially movable shaft from a switch actuator during normal operation of an electrical control.

Accordingly, it is an object of the present invention to provide a new and improved electrical control having the various desirable features set forth above. Another object of the present invention is to provide new and improved means that prevent separation of a shaft from a switch actuator. Still another object of the present invention is to provide a new and improved electrical control wherein a centrally positioned cam surface and spring means insure a balanced contact pressure between a bridging contactor and a pair of the stationary contact surfaces. A further object of the present invention is to provide a new and improved electrical control wherein an axially movable switch actuator is also rotatable so as to facilitate adjustment of a variable resistance control combined therewith. A still further object of the present invention is to provide a new and improved electrical control wherein spring means operate to provide fast and crisp movement of a bridging contactor relative to a pair of stationary contact surfaces. Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification. v

Briefly, the present invention is concerned with an electrical control which employs a'bridging contactor that is movable between a' first stable position wherein it engages at least one stationary contact surface and a second stable position wherein it is spaced from such contact'surfa ce. In a preferred embodiment, the bridgingcontactor is a cylindrical contact roller having a pair of end portions engageable with spaced stationary contact surfaces, a central portion engageable with a switch actuator, andportions between the central portion and end portions that are engage'able by biasing means. Preferably, the biasing means is one or more coiled compression springs. In operation, a first cam surface on the switch actuator moves the contact roller against the bias of a spring. With continued movement of the switch actuator, the spring reaches a condition of maximum compression, the roller reaches a position of maximum lateral displacement, the spring decompresses, the roller moves to a labile neutral position, and the spring whips the contact roller along a second cam surface on the switch actuator. While the switch actuator is moving, the spring is free to shift tangentially relative to the contact roller and assume contorted configurations. With such shifting,the contact points between the roller and spring move and change the pressure angle between the contact roller and spring. With the changing pressure angle, the spring holds the contact roller against either an abutment or stationary contact surface while the contact roller is moving toward and away from positions of maximum lateral displacement and while the spring is compressed and subsequently decompressed. Then, as the spring whips the contact roller along the second cam surface, the spring assumes a changed contorted configuration and drives the contact roller to a stable position. In a preferred embodiment, means interlock the switch actuator and an axially movable shaft. In another embodiment a switch actuator is rotatable as well as axially movable. In still another embodiment, a switch actuator and shaft snap together, and means prevent the shaft from subsequently being pulled away from the actuator, preferably, such last-mentioned means comprise walls formed in an element which trap the actuator and prevent a pair of jaws on the actuator from releasing a reduced diameter portion of the shaft.

For. a better understanding of the present invention, reference may be had to the accompanying drawings wherein the same. reference numerals have been applied to like parts and wherein: FIG. 1 is an isometric view of a combination variable resistance and electricalswitch control embodying the present invention; FIG. 2 is an exploded view of the control shown in FIG. 1 and includes a schematic representation of the location and direction of forces acting on one of .the il- I lustrated contact rollers when in a stable position thereof; FIG. 3 is a sectional view taken along lines III-III of FIG. 1; FIGS. 4-11 are fragmentary sectional views of the control of FIG. 1 and schematically illustrate the relative positions of a contact roller, spring, and switch actuator as the contact roller is moved between first and second stable positions thereof; FIG. 12 is a fragmentary sectional view of another embodi- ,ment of the present invention; FIG. 13 is an exploded isometric view of parts of the structure illustrated in FIG. 12; and 7 ears interfit with notches 28, 29 formed in a switch housing 30. The variable resistance control 22 includes a threaded mounting'bushing 31 suitable for insertion through an aperturein a mounting panel. A locating ear 32 secured to the control cooperates with a dimple or opening in such panel and prevents rotation of the electrical control 21 when a not shown locknut is threaded onto the bushing 31. In addition, the variable resistance control includes an insulating base 33 with a resistance element 34 secured thereto, a center collecto r 36, and a plurality of terminals 37-29 connected to the center collector and the ends of the resistance element as best shown in FIG. 2. A wiping contactor 41 is constrained to rotate with a contactor driver 42 and wipingly engages the center collector 36 and resistance element 34 intermediate the ends thereof. In order to move the driver 42, a shaft 43 is provided with a flatted portion 44 for drivingly engaging an aperture 46 in the driver. When the variable resistance control 22 is assembled, tabs 47, 49, 51 are folded over notches 52, 53, 54 in the insulated base 33 and the end 56 of the shaft 43 projects through an opening 57 formed in the bottom of the cover 27.

The switch 23 includes the previously mentioned housing 30, a pair of substantially identical helical compression springs 61, 62 a pair of substantially identical cylindrical contact rollers 63, 64, and a switch actuator 66 having a pair of double surfaced cams 67, 68 and a pair of jaws 69, 71 that interfit over the end 56 of the shaft 43. A pair of alignment arms 72, 73 on the switch actuator 66 are slidably received within a pair of slots 74, 76 formed in the housing .30 and facilitate assembly of the actuator and housing. Anchored in'the housing 30 are four terminals 77, 78, 79, and 81 The upper ends of these terminals 77a, 78a, 79a, 81a provide spaced stationary contact surfaces within the housing that are bridged by the contact rollers 63 and 64 when the switch is in a closed switch condition. In order to retainthe springs 61, 62.properly positioned in the housing 31 during operation, seats 82 and 83 formedin the ends walls of the housing receive the end portions 61a, 62a of the springs. Although the rear wall 84 of the cover 27 may be used to retain'the contact rollers and springs within the housing 30 after assembly, it is preferred that a separate cover 86 be used for this purpose. A centrally disposed opening 87in such cover permits the passage therethrough of the end 56 of the shaft and the jaws 69, 71 of the actuator 66. Means illustrated as shoulders 88, 89 and peripheral wall 91 formed on the switch housing 30 position the cover 86 on the housing.

Any suitable materials may be used to fabricate the abovementioned parts of an electrical control embodying the invention and in the illustrated control 21, the terminals and contact rollers were formed of an electrically conductive material, i.e., copper covered with a thin coating of silver to improve the solderability of the terminals and retardthe formation of oxides on the contact surfaces. Phenolicor one of other materials too numerous to mention is used to fabricate the housing 30. essentially the only criteria for selection being that the housing be made of a materialthat will satisfactorily insulate the terminals 77 78, 79, 81 from one another.

When the switch and variable resistance control areassembled together as shown in FIG. 3, the actuator 67 is axially movable along a line defined by the axis of rotation of the shaft 43, i.e., in the direction represented by the arrow A. With the contact rollers in the illustrated closed switch or first stable position, the actuator is in a corresponding first stable position with the cam faces 67a, 68:: hearing against the con tact rollers. In this position, the springs 61, 62 are at least slightly compressed and slightly contorted, i.e., held ina configuration other than single compression wherein adjacent convolutions of each spring proximate the the contact surfaces 79a, 78a are spaced more closely together than the adjacent convolutions of the springs distal from such contact surfaces. While the contact rollers are in the first stable position, the jaws 69, 71 of the actuator 66 are received within the wall 92 of the driver 42 which is free to rotate relative to the actuator. However, the jaws 69, 71 of the actuator 66 are received within the wall 92 of, the driver 42 which is free to rotate relative to the actuator. However, the jaws 69, 71 are spaced close enough to the wall 92 to prevent the jaws 69, 71 from opening to release the reduced diameter portion 56a of the shaft wen an axial pullout force is applied to the shaft 43 as will be more fully described hereinafter in the detailed description of the embodiment illustrated in FIGS. 12 and 13.

The improved operating characteristics of the electrical control 21 will be best understood by now having reference to FIGS. 4-1l which clearly illustrate the sequence of operation of the control 21 as the contact rollers move from a first stable position shown in FIG. 4 to a second stable position shown in FIG. 8 and-then move back toward the first stable position in response to movementof the actuator 66. FIGS. 411 have been presented for purposes of discussion only, and such figuresare schematic representations of the control but it will be understood that the following description pertains to'single or double pole, and single or double throw devices. The point P in FIGS. 4-11 generally represents a movable point of contact at the interface of the spring 62 and contact roller 64 and it will be appreciated that the pressure angle between the spring and roller,i.e., the angle defined by the intersection of a line passing through the point P and the center of the contact roller 64 with a horizontal line passing through the center of the contact roller, changes as the contact roller 64 moves between the two stable positions thereof. In other words, the point P moves as the contact roller moves between such stable positions. It will also be appreciated that in the control 21, two such contact points exist where the end convolutions 61b and 62b bear against the contact roller. In F IG. 2 these points have been identified on the contact roller 64 by the points? and P.

In the first stable position shown in FIG. 4 the contact roller 64 is biased by the spring 62 into a wedge shaped area defined by the cam surface 670, stationary contact surface 77a and not shown stationary contact surface 78a. In this position, the spring 62 biases contact roller 64 both downwardly against the stationary contact surfaces and laterally against the cam surface 67a. The center axis of the spring 62 as well as the upper and lower edges of the spring'as viewed in FIG. 4 are curved, and to distinguish such curvature or nonuniform compression of the spring from a uniformly compressed configuration, the spring will be referred to as being contorted as well as compressed. As the actuator 66 is moveddownwardly to the position illustrated in FIG. 5, the contact roller 64 is-displaced outwardly along the stationary contact surface 77a,to-:a position of maximum lateral displacement at which point thecenter of the contact roller is horizontally aligned with the apex of the cam. In this figure of the drawings, the spring has assumed a since the end convolution 62b of the springhas-shift'ed upwardly toward the cover 8 6--and"effected an upward shift of the contact point P. During movement. of thecontact roller between the positions shown in FlGS. 4 and 5 the roller normally may either roll'or slidealong the stationary contact surfaces. In either case, goodelectrical continuity and a satisfactorily low contact resistance is maintained between the stationary .contact surfaces and contact roller because of the downwardly directed bias of the spring 62.

Further movement of-the actuator 66 to the position shown in FIG. 6 permits the spring-62 to decompressand reduce the amount of lateral displacement of'the contact roller'relative to the apex of the cam 67. During this decompression, spring6'2 changes to a third contorted configuration and the pressure angle increases to a maximum value. Because ofthis'change in pressure angle, i.e., tangential shift of the end convolution62b of the spring relative-to the contact roller'64, the'contact roller is still held proximate to the stationary'contact surfaces even through the apex of thecam-67has moved to a position below a horizontal line passing through the center of the contact roller. When inthe reduced displacement position of FIG. 6, the contact roller=64 is in a labile neutral position; it being understood that as it applies to-the present illustrated embodiment, this term does' not define the position of maximum lateral'displacement of' thecontact'roller 64 or the minimum compressed length of-the spring'62': When the actuator'tifi is moved an infinitesimalamount from the position of FlG.6 to theposition of FIG. 7,;the contact roller'6'4 rapidly moves upwardly along' the cam surface67'b; The movement of the contact rollerl64 and spring 62 is surprisingly rapid" and crisp,. an'd the spring snaps fromthe contorted configuration shown in ,FlG. 6 to thecon'figurations-sho'wn'inFlG: 7 and shownin F 16. i 8 whereinthecontact roller-64has attained the second stable position thereof. Asithe spring 62-snapsfrom thethird configuration (FlG.6) to'thejfourth configurationTFlG. 7) the endconvolution: 6250f the-spring shifts tangentiallyrelative'to the contact roller-andthep'oint Pshifts to a" position positionss'howninFlGS. 9 -11 until-the first stablepo'sition'isonce again-reached. Howevenit'should'be noted that the contact'point P hasshifted successivelyldownwardlyin FlGS. 9' and 10 and that'the pressure angle'becomes positive once again as the spririg GZ-whips from thelabile neutral contorted configuration shown-in'FlG. 10 totheconfigurationillustrated in 'FlG. 11. As thespringbiases the contact roller 64toward the first'stable position, the downwardly-directedthrust of the spring greatly inhibits and in fact substantially eliminates bouncingof-the-contactroller as itengagesthe stationary contact surfaces. 5

' A clear-advantage of controls embodying thisinvention is that an extremely large-movable contact. surface 'isavailable for engagement with the stationary contactsurfaces andyje't such controls'occupy" no more spac'e'than the'controls available heretofore. More specifically, the actual contact surface (per unit width of the stationary contact surfaces) available for consumptionduring. the life of the control .21" is approximately 3.14 titties the diameter of the contact roller 64'.-

Although the'foregoing descriptioii has not emphasized ,the fact. that the contact roller 64=normallyiolls along thestatiionary contact surfaces as-it movesfrom' the first .tothe secondstable positionyextensive tests have shown that nor-' mal ly 'the contact roller actually rolls along the stationary contact surfaces. This condition'contributes to extended contactor life since the contactor will then pry apart any welds along the interface of the movable and stationary contact'surfa'ces as well as move'a diffren't'Surface portion of the contact roller "64 into engagement with the stationary-contact surfaces on each successive actuation. 'AFter hundreds of thousands of actuations, when the movable and stationary coiit'a'ctsurfaces have started to become worn, irregularities in the contact surfaces tend to provide a geared action and actually promote rolling of the contact roller along the stationary contact surfaces. A comparison of the'changing relative positions of the Contact roller and stationary contact surfaces in FIGS. 411 reveals that the contact roller makes and breaks contact with the'sta'tiona'rycontact surfaces at two different locations along thestationary contact surfaces. This feature also contributes 'tolonger life of the switch and satisfactory operation of the control-21 'under'high loador other adverse operating conditions.Morespecifically, the contact roller 64 breaks contact with the stationary contact surfaces at an outwardly displaced position of the contact roller and any {arcing that occurs between the'stationary and movable contact surfaces causes pitting or other degradation of the stationary contact surfaces in the'region where the contact roller engages the stationary contact surfaces just prior to movement to the second stable position. Then, as the contact roller moves back to the first stable position, it initially "engages the/stationary contact surfaces along aregion under the'cam face 67a and then moves laterally toward'the actuator and into'the first stable position shown irrFlG.-4..

Theprobiem of insufficient'pressure between the stationary and movable contact surfaces because of the presence of foreign matter between one of the stationary contact surfaces and thecontact roller,- or because of uneven contact pressure occasionedby other factors, is also over come by the particular spatial relationship of the actuator, cori'tact roller, and stationary contact surfaces. ln FIG. 2, the arrows B, C represent the approximate direction of the forces applied to the roller 64 bythe'spring 62in'the'first stable position. Similarly arrows D, E andF represent the reaction forces exerted by the stationary contact surfacesand the actuator upon the roller. Since the reaction forces D, E are appliedto end portions of the roller, thereactionforce'F is appliedto the central portion of the roller, and'a dynamicor resilientbiasing force B or C is apipliedto the rollerbetwee'n'the centr'alp'o'rtion and each end portion thereof, 'the contact roller is self-balancing during operation. Thus, if a roughe'ned contactsurface or particle of foreignma'tter causes o'n'e end of the contact roller to seat abpresent invention and thereby attain the;advantages thereof.

For example, although the springs are illustrated as being coiledelements, other spring means,such as leaf spring, box springs, or spherical orcircular resilient discs could be used to accomplish the objects of the present invention. Similarly, the bridging'contactor could'be an element other than a hollow cylinder although'it is definitely preferred that'the external configuration be such that the bridgingcpntactor will readily roll across-at least one of the stationary contact surfaces.

ln FIGS. 12 and 13 a modified switch actuator 95, shaft 96, and driver 97"'coop'erat'e to perm'itaxialplug-in assembly of the shaft and actuator. During assembly 0f the shaft 96 with the actuator 95, a tapered locking lug 101' is axially inserted between the jaws 98,99 which resiliently yield and then snap together with the lips 103, 104 engaging the shoulder 106 of 101 on the shaft by the wall 113. This antipullout feature, as

trated in FlG. 1.

Stillanother modification is shown in FIG. l4'wherein the contact rollers 63, 64 have beenshown in operable relationship with a switch actuator 116 fixedly secured to shaft 117. When the actuator 116 is formed integrally with the shaft 117 as illustrated, the material used in fabrication of the shaft and actuator must be an electrically nonconductive material such as nylon in order to prevent an electrical short circuit between the bridging contactors 63 and 64. Since the actuator 1 16 has only two continuous camming surfaces 116a and 116b, the actuator is continually rotatable with the shaft and also axially movable for moving the contact rollers between the first and second stable positions thereof. The flatted portion 119 of the shaft '117 interfits with a flatted driver that may be substantially the same as driver 42 or driver 97. This embodiment of the invention is particularly suitable in applications wherein an electrical control having a minimum number of parts is desired and yet wherein all of the advantages and desirable characteristics of the previously described embodiments are retained. I

While there has been illustrated and described what is at present considered to be a preferred embodiment of the present invention and several modifications thereof, it will be appreciated that numerous changes 1 and modifications are likely to occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall with the true spirit and scope of the present invention.

What I claim as new and desire to be secured by Letters Patent of the United States is: H

1. An electrical control comprising a housing, a first stationarycontact surface fixedly positioned within the housing, a second stationary contact surface spaced from the first contact surface and fixedly positioned within the housing, an acpreviously mentioned, is also present in the embodiment illustuator having a cam surface and movable between at least two stable actuator positions along a predetermined path, a cylindrical contact roller movable to a first stable contact roller position wherein the contact roller is biased against said contact surfaces thereby to establish .an electrical connection between said contact surfaces thereby to establish an electrical connection between said contact surfaces and movable to a second stable roller position wherein the contact roller is physically spaced from at least one of said contact surfaces, a spring means for wedging the contact roller between said cam surface and said contact surfaces, said spring means having a first portion thereof seated in the housing, a second portion bearing against and compressively engaging the contact roller,

and a third resilient portion extending between said first and second portions, said resilient portion having energy stored therein while the contact roller is in the first stable position, initial movement of the actuator from a stable position thereof corresponding to said first contact stable roller position effecting movement of the contact roller along the cam surface and said contact surfaces to a position of maximum lateral displacement relative to the actuator, such movement of the con- 2. The electrical control of claim wherein the second portion of the spring means maintains bearingcontact with the surface of the contact roller at substantially two points thereby to reduce frictional forces between the I contact roller and spring and permit the spring means to assume contorted configurations. I i v 3. The electrical control of claim 1 where the second portion of the spring means shifts tangentially relative to the contact roller when the contact roller moves fi 'om theposition of maximum lateral displacement lateral displacement.

4. The electrical control of claim 1 wherein the pressure angle between the spring means and contact roller increases as the contact roller moves from the first stable position to the labile neutral position thereof.

5. The electrical control of claim 1 wherein the spring means is a coiled helical element having a central axis substantially normal to said predetermined path, the second portion of the spring means comprises an end convolution of the helical element, and the spring means has a contorted configuration when in the partially decompressed condition, said contorted configuration being defined by adjacent convolutions on the side of the spring means proximate to the stationary contact surfaces being disposed in closer proximity to each other than the adjacent convolutions on the side of the spring means distal from the stationary contact surfaces, the contorted configuration causing the spring means to cock as the contact roller reaches the first labile neutral position thereof and whip the contact roller to the second stable position thereof as the side of the spring means proximate to the stationary contact surfaces expand.

6. The electrical control of claim 1 wherein the control includes a rotatable and axially movable shaft, a resistance element, and a contactor wipingly engaging the resistance element and constrained to rotate with the shaft, axial movement of the shaft causing movement of the actuator along said predetermined path.

7. The electrical control of claim 6 wherein the actuator includes a pair of closed. jaws disposed in an interlocking arrangement with the shaft and the control further comprises means for holding said jaws closed when a pullout force is applied to said shaft.

8. The electrical control of claim 7 wherein the shaft includes a locking lug, the jaws are closed around the locking to the position of reduced lug, and the means for holding comprise a driver having an intact roller causing the spring means to assume a condition of maximum compression, further movement of the actuator effecting further movement of the contact roller to a position of reduced lateral displacement corresponding to a first labile neutral position of the contact roller, such further movement of the contact roller causing the spring means to assume apar- -tially decompressed condition, still further movement of the actuator causing the spring means to whip the contact roller to the second stable position thereof.

ternal wall surrounding the is applied to the shaft.

9.,The electrical control of claim 6 wherein the actuator and shaft are formed integrally with each other and wherein the actuator moves axially and rotates in response to axial and rotary movement of the shaft.

10. In an electrical control, the combination of a housing, resistance means within the housing, a driver disposed in the housing, means carried by the driver for making wiping con tact with the resistance means, at least one pair of stationary contact surfaces, at least .one cylindrical contact roller movable between two stable positions and into and out of engagement with at least one of said stationary contact surfaces, a switch actuator engageable with the contract roller, spring means bearing against the contact roller for urging the contact roller against both of said stationary contact surfaces, and means for moving the driver relative to the resistance means and for moving the switch actuator between first and second stable positions.

1 l. The electrical control of claim 10 wherein said last mentioned means comprises a rotatable and axially movable shaft jaws at least when a pullout force and the actuator includes a pair of jaws interfitting with said through the aperture, and the actuator includes a pair of jaws interfitting with the shaft, said jaws being disposed within the retaining wall when the contact roller is in at least one of the stable positions thereof whereby the retaining wall prevents the jaws from opening and releasing the shaft when a pullout force is applied to the shaft.

13. The electrical control of claim 10 wherein the last mentioned means comprise a rotatable shaft secured to the switch actuator and the switch actuator is provided with two continuous cam surfaces engageable with the contact roller, said actuator being rotatable and axially movable with said shaft.

14. An electrical control comprising at least one abutment surface, a pair of stationary contact surfaces, an actuator movable between first and second stable actuator positions, at least one cylindrical contact roller movable to a first stable roller position as the actuator is moved to the first stable actuator position and movable to a second stable roller position as the actuator is moved to the second stable actuator position, an spring means having an end portion seated within the housing and a bearing portion compressively engaging the surface of the contact roller, said spring compressively biasing the contact roller against the pair of stationary contact surfaces in the first stable roller position and compressively urging the contact roller against said at least one abutment surface in the second stable roller position, said roller having a pair of end portions engageable with the stationary contact surfaces, a central portion engageable with the actuator, a first portion between the central portion engageable with the actuator, a first portion between the central portion and one of the end portions engageable with the spring means, and a second portion between the central portion and the other one of the end portions engageable with the spring means whereby .the contact roller engages the stationary contact surfaces with a balanced contact pressure.

15. The electrical control of claim 2 wherein said .two points are spaced a distance greater than the diameter of said contact roller.

16. The electrical control of claim 15 wherein said cam surface and said second portion engage said contact roller at points spaced from each other and spaced from the points of engagement of the contact roller and the contact surfaces.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION P n 3,600 ,533 Dated Au ust 17, 1971 Invent0r(s) JACK A. ENGLISH It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Specification:

Column 2, Line 3; Delete one of the words "to".

Column 2, Line 71; After the word "pulled" and before the word "away", add the word "axially".

Column 4, Line 18; Change the word "single" to -simple-.

Column 4, Lines 26, Delete the sentence "However, the jaws 69,

27, & 28; 71 of the actuator 66 are received within the wall 92 of the driver 42 which is free to rotate relative to the actuator.

Column 4, Line 30; Change the word "wen" to -when.

Column 5, Line 21; Change the word "through" to ---though-.

Column 6, Line 6; Change the word "AFter" to -After--.

In the Claims:

Column 7, Lines 50 Delete the words "thereby to establish an & 5].; electrical connection between said contact surfaces",

Column 9, Line 19; Change the word an to and-.

Signed and sealed this 29th day of May 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents QRM 10459) USCOMM-DC 50376-P69 Q U 5, GOVERNMENT PRINTING OFFICE: 959 0-365-33 

1. An electrical control comprising a housing, a first stationary contact surface fixedly positioned within the housing, a second stationary contact surface spaced from the first contact surface and fixedly positioned within the housing, an actuator having a cam surface and movable between at least two stable actuator positions along a predetermined path, a cylindrical contact roller movable to a first stable contact roller position wherein the contact roller is biased against said contact surfaces thereby to establish an electrical connection between said contact surfaces thereby to establish an electrical connection between said contact surfaces and movable to a second stable roller position wherein the contact roller is physically spaced from at least one of said contact surfaces, a spring means for wedging the contact roller between said cam surface and said contact surfaces, said spring means having a first portion thereof seated in the housing, a second portion bearing against and compressively engaging the contact roller, and a third resilient portion extending between said first and second portions, said resilient portion having energy stored therein while the contact roller is in the first stable position, initial movement of the actuator from a stable position thereof corresponding to said first contact stable roller position effecting movement of the contact roller along the cam surface and said contact surfaces to a position of maximum lateral displacement relative to the actuator, such movement of the contact roller causing the spring means to assume a condition of maximum compression, further movement of the actuator effecting further movement of the contact roller to a position of reduced lateral displacement corresponding to a first labile neutral position of the contact roller, such further movement of the contact roller causing the spring means to assume a partially decompressed condition, still further movement of the actuator causing the spring means to whip the contact roller to the second stable position thEreof.
 2. The electrical control of claim 1 wherein the second portion of the spring means maintains bearing contact with the surface of the contact roller at substantially two points thereby to reduce frictional forces between the contact roller and spring and permit the spring means to assume contorted configurations.
 3. The electrical control of claim 1 wherein the second portion of the spring means shifts tangentially relative to the contact roller when the contact roller moves from the position of maximum lateral displacement to the position of reduced lateral displacement.
 4. The electrical control of claim 1 wherein the pressure angle between the spring means and contact roller increases as the contact roller moves from the first stable position to the labile neutral position thereof.
 5. The electrical control of claim 1 wherein the spring means is a coiled helical element having a central axis substantially normal to said predetermined path, the second portion of the spring means comprises an end convolution of the helical element, and the spring means has a contorted configuration when in the partially decompressed condition, said contorted configuration being defined by adjacent convolutions on the side of the spring means proximate to the stationary contact surfaces being disposed in closer proximity to each other than the adjacent convolutions on the side of the spring means distal from the stationary contact surfaces, the contorted configuration causing the spring means to cock as the contact roller reaches the first labile neutral position thereof and whip the contact roller to the second stable position thereof as the side of the spring means proximate to the stationary contact surfaces expand.
 6. The electrical control of claim 1 wherein the control includes a rotatable and axially movable shaft, a resistance element, and a contactor wipingly engaging the resistance element and constrained to rotate with the shaft, axial movement of the shaft causing movement of the actuator along said predetermined path.
 7. The electrical control of claim 6 wherein the actuator includes a pair of closed jaws disposed in an interlocking arrangement with the shaft and the control further comprises means for holding said jaws closed when a pullout force is applied to said shaft.
 8. The electrical control of claim 7 wherein the shaft includes a locking lug, the jaws are closed around the locking lug, and the means for holding comprise a driver having an internal wall surrounding the jaws at least when a pullout force is applied to the shaft.
 9. The electrical control of claim 6 wherein the actuator and shaft are formed integrally with each other and wherein the actuator moves axially and rotates in response to axial and rotary movement of the shaft.
 10. In an electrical control, the combination of a housing, resistance means within the housing, a driver disposed in the housing, means carried by the driver for making wiping contact with the resistance means, at least one pair of stationary contact surfaces, at least one cylindrical contact roller movable between two stable positions and into and out of engagement with at least one of said stationary contact surfaces, a switch actuator engageable with the contract roller, spring means bearing against the contact roller for urging the contact roller against both of said stationary contact surfaces, and means for moving the driver relative to the resistance means and for moving the switch actuator between first and second stable positions.
 11. The electrical control of claim 10 wherein said last mentioned means comprises a rotatable and axially movable shaft and the actuator includes a pair of jaws interfitting with said shaft thereby to permit rotation of the shaft relative to the actuator and to limit axial movement of the shaft relative to the actuator.
 12. The electrical control of claim 10 wherein the driver is provided with a centrally located aperture, and a centrally located retaining wall, The means for moving the switch actuator comprises a rotatable and axially movable shaft extending through the aperture, and the actuator includes a pair of jaws interfitting with the shaft, said jaws being disposed within the retaining wall when the contact roller is in at least one of the stable positions thereof whereby the retaining wall prevents the jaws from opening and releasing the shaft when a pullout force is applied to the shaft.
 13. The electrical control of claim 10 wherein the last mentioned means comprise a rotatable shaft secured to the switch actuator and the switch actuator is provided with two continuous cam surfaces engageable with the contact roller, said actuator being rotatable and axially movable with said shaft.
 14. An electrical control comprising at least one abutment surface, a pair of stationary contact surfaces, an actuator movable between first and second stable actuator positions, at least one cylindrical contact roller movable to a first stable roller position as the actuator is moved to the first stable actuator position and movable to a second stable roller position as the actuator is moved to the second stable actuator position, an spring means having an end portion seated within the housing and a bearing portion compressively engaging the surface of the contact roller, said spring compressively biasing the contact roller against the pair of stationary contact surfaces in the first stable roller position and compressively urging the contact roller against said at least one abutment surface in the second stable roller position, said roller having a pair of end portions engageable with the stationary contact surfaces, a central portion engageable with the actuator, a first portion between the central portion engageable with the actuator, a first portion between the central portion and one of the end portions engageable with the spring means, and a second portion between the central portion and the other one of the end portions engageable with the spring means whereby the contact roller engages the stationary contact surfaces with a balanced contact pressure.
 15. The electrical control of claim 2 wherein said two points are spaced a distance greater than the diameter of said contact roller.
 16. The electrical control of claim 15 wherein said cam surface and said second portion engage said contact roller at points spaced from each other and spaced from the points of engagement of the contact roller and the contact surfaces. 